BQ34Z100-G1: Chemical ID selection

Hi Nick, 

I am a colleague of LUO. After I finished the battery data of GPC, I got the report as shown in the figure.

Does this mean there is something wrong with the data I submitted? How should I get a CHEM ID that suits me?

This is the data I submittedLFP.zip

Hi Nick, 

Following your advice, I successfully obtained the recommended CHEM ID, but now I still encounter two problems after learning cycle, please help me judge the cause of the problem.

1.FCC>Design cap but SOH = 97%

2.After discharge, PASSCHARGE>CC threshold, cycle count will not change.

Here is my gg.file and my log, sincerely hope to get your answer.

0602_48V3.gg.csvSI-log-2023-06-02-09-20-55-dev1.csv

Hello Kent,

Are you using a scaling factor for the current, as I see that you have a discharge of over 100 amps.

The FCC being greater than your design capacity seems fine because your Qmax and Design Capacity
are slight different.

Are you able to get a BQStudio log for the gauge. I want to make sure you are pulling data from the correct
registers. What brings up a concern for me is the Ra table in your gg file. The values are very
high, which is why I am asking for a BQStudio log.

Also, can you send me the schematic of your circuit.

How many sets of cells are in parallel?

Sincerely,
Nick Richards

Hi 

Thank you for your patience. 

1. My current sf=10

2. It is normal for the discharge current over 100A, the battery pack I use is 14s 6p, so there will be a fully charged voltage of 49V and a discharge current of 100A.

3.I use 9A to fully charge the battery pack to FC and wait for OCVtaken, then use 1C current to put the battery pack to Cell Terminate Voltage (the cut-off voltage may not be collected due to the sampling interval), and wait for OCVtaken as a learning.

My SOC did not become 0 after the end of discharge

cycle count increased but Maxerror was still 1

SOH was 100 but how do I choose the proper SOH LOAD I

The following is my learning cycle LOG and ggfile, and the record was interrupted once due to poor equipment contact.

The problem that the SOC cannot be smoothed to 0 after using high current discharge and the MAXerror does not increase needs your help.

BQSTUDIO.csv

BQSTUDIO2.csv

0606.gg.csv

Hello Kent,

SOH LOAD I should be set to the discharge current that the gauge usually experiences.

I will need some time to look at the files you sent and will hopefully get back with you tomorrow.

Sincerely,
Nick Richards

Hello Nick,

I have to thank you again for your patience in answering.

With your help I successfully solved the problem of MaxError.

But I still have a question about SOC that I want to ask, The reason why I mentioned in your answer that the SOC of my LOG is 11 is that the voltage is still 33.74V but when I checked, I found that the voltage read by BQ34 in the LOG seems to have reached 30.828V, maybe you said 33.74V It's not the voltage of BQ34 but the voltage at the MCU. It's a mistake in the mark when I sent the data.

I will try to increase the Cell Terminate Voltage according to your suggestion. At the same time, I want to know what effect will be caused by modifying LOAD SELECT. I am currently using LOAD SELECT=6, 3000mA. If I increase or decrease this value, what effect will it have? .

I tried to use LOAD SELECT=1-Present average discharge current yesterday, but I found that my FCC will drop from 7400mAh to 1200mAh immediately after modification, and only 1200mAh after learning, why?

Thanks again for your answer

Hello Nick,

I changed the User_Rate_mA from 3000 to 12000 according to your suggestion, as my understanding this will make the SOC drop faster during the discharge, thus having a lower SoC value at the end of the discharge.

However, in my observation, FCC is larger than User_Rate_mA=3000 after learning, but SOC still jumps from 13 to 0. My ideal situation is to control the SOC value at the end of discharge within 5. Is there anything else you think I can modify to achieve this goal, can you list it for me? 

Now I want to try to modify T rise, ResRelax Time try to use Fast Scale, I don't know what effect these will have.

I attach the ggfile and log data used in this test, forgive me for not being able to use BQSTUDIO to record data during high current discharge, I need to take heat dissipation into consideration. Because the LFP battery takes too long to do one learning cycle, I have no way to consider a plan that requires multiple studies.

Looking forward to your reply.

0609-12000.gg.csv

0609-12000mA.csv

Hello Kent,

Is the log file you sent showing data right after you changed the "User_Rate_mA"? Whenever you
change any parameter related to Load Select or Load Mode, the gauge is creating new simulations
to calculate SoC. However, the gauge will need time to learn the proper model for the battery.
Therefore, I would recommend cycling the battery a few times to see if that fixes the reading of
SoC. In the log file, I see that FCC is still changing a lot, which shows that the gauge is still
correcting itself on the true FCC of the battery.

ResRelax time deals with resistance updates. I would recommend not changing any of those setting
just yet and lets see if the gauge can correct itself after a few cycles of the battery. Make sure
that the battery have enough relaxation time after charge and discharge.

Sincerely,
Nick Richards

Hello Richards,

Thank you very much for your suggestion. I have performed many LEARNING CYCLE. Although the first few times I successfully reduced the SOC from 14 to 10, the FCC also dropped significantly to 7230mAh. Unfortunately, after that, the learning is no longer effective. Every time After discharging, the SOC is around 10 every time.

I rummaged through the LOG data, I have been charging and discharging with full load for LEARNING CYCLE, the released capacity is 6500mAh, but after many times of learning, my FCC will never be lower than 7000mAh, so that my SOC will always jump to 0.

I have never used LEARNING CYCLE with light load, but discharge with light load can discharge 7100mAh, so that the SOC jumps to 0 at a lower value. I know this is the difference in discharge power caused by the battery being discharged with different loads, but I would like to ask, is there any way to make the SOC curve of BQ34 closer to my full-load discharge situation, so I can discard part of the light-load discharge accuracy.

In addition, the User_Rate_mA I am using now is the average current when I discharge at full load. According to my understanding, the SOC should be in line with my current full-load discharge.

Can you please help me to solve the above doubts?

The following is the data I used to discharge with light load before, and the data of full load discharge after I have learned many timesDSG_LOG.csv

full load.csv

Hello Kent,

Can you send me the gg file for your current setup?

It is possible that completing the learning cycle with the discharging at full load can affect the Ra table during the process. Therefore, I would recommend you to complete one new learning cycle, using a discharge rate of C/5 (discharging at 1440 mA).  After you successfully complete this learning cycle, please also send me the gg file for that setup. I will need both gg files to analyze the changes.

Sincerely,

Nick Richards

Hi Richards,

Here is my gg.file, plz help me to point out the problem!

Thanks

full load.gg.csvlight load.gg.csv

Hello Kent,

I will need some time to review the files you sent, and should get back with you soon.  

Sincerely,
Nick Richards